Tratamento e avaliação de desempenho de discos de freios de protótipo baja nitretados à plasma

Abstract

This work aims to demonstrate how to increase the surface hardness, impact resistance, wear resistance and provide a longer service life to a brake disk, made of drawn AISI 1045 steel, submitted to plasma nitriding. Using a gas mixture of 20% hydrogen (𝐻2) and 80% nitrogen (𝑁2), the influence of treatment time and temperature in four different nitriding conditions were evaluated. Nitriding I lasted 3 hours and at a temperature of 450 ºC, II lasted 4 hours at 450 ºC, III 4 hours at 500 ºC and IV 4 hours at 400 ºC. Treatments I, II and III took place at a pressure of 0.8 mBar, in a direct current source. For comparative effect due to the complex geometry of the brake discs, IV treatment was performed at a pressure of 2 mBar using a pulsed current source. The properties of the nitrided layers obtained in the samples were evaluated by means of surface microhardness, microhardness profile, X-ray diffractometry and wear test carried out in situ in an off-road prototype of the baja type from UFERSA. The results showed an effective improvement in performance, with a significant reduction in disc wear, notably in conditions III and IV, directly related to the thickness and uniformity of the nitrided layers, as well as to the significant increase in icrohardnesses in relation to the standard material. Therefore, validating the plasma treatment of brake discs as a technological alternative.